This invention relates to the field of intraluminal support devices such as stents and the like. Typically, stents are expandable, tubular metallic devices that are positioned within a patient""s vasculature or other body lumen and expanded in order to support a vessel or body lumen at a desired intraluminal location to allow the flow of blood or other body fluids therethrough. Often, the stents are formed from a deformable metal and delivered to the desired intraluminal location by mounting the stent onto an expandable portion, e.g. a balloon, on the distal extremity of a delivery catheter. By advancing the catheter through the body lumen, the stent may be delivered to a desired position and expanded therein by expanding the balloon to an expanded configuration, seating it within the artery or other body lumen. Other implementations make use of a self-expanding stent formed from a suitable material such as pseudoelastic material that is delivered in a constricted condition and when released spontaneously expands to an enlarged configuration. A stent made of superelastic alloy (e.g. NiTi alloy) may be inserted into the body lumen with a stress induced martensitic phase and expanded within the body lumen. Further details of stents and stent delivery systems may be found in U.S. Pat. No. 5,507,768 (Lau et al.), U.S. Pat. No. 5,458,615 (Klemm et al.), and U.S. Pat. No. 5,514,154 (Lau et al.), incorporated herein by reference in their entireties.
Stents are often used in conjunction with an intravascular treatment for conditions such as obstructive coronary artery disease and peripheral artery disease. For example, ablation, atherectomy, balloon dilation, laser treatment or other procedures are among the methods used to widen a stenotic region of a patient""s vasculature. However, restenosis occurs in large percentage of percutaneous transluminal coronary angioplasty (PTCA) patients and rates can be even higher with other procedures. Restenosis is thought to be a natural healing reaction provoked by injury from the intravascular procedure. The healing process frequently causes thrombosis and may lead to intimal hyperplasia that occludes the vessel. The prior art has employed a number of mechanical and pharmacological strategies to reduce the restenosis rate, but none have been particularly effective. Accordingly, stents have been proposed to maintain the patency of a treated vessel and reduce restenosis. Using stents, restenosis rates have fallen to less than 20%. Although helpful in reducing restenosis, stents do not represent a complete solution. The framework of the stent may still allow migration and proliferation of the smooth muscle cells, while the stent itself can be thrombogenic. To address these problems, stents have been provided with covers made from various materials such as DACRON, polytetrafluoroethylene (PTFE), heterologous tissue and autologous veins, arteries and tissue.
It would be a significant advance to provide a stent with an improved connector for securing a cover to the stent. This invention satisfies these and other needs.
The invention is directed to a stent suitable for maintaining the patency of a bodily lumen, generally comprising a tubular body configured to facilitate connection of a cover thereto. A stent assembly of the invention generally comprises a stent having at least one cover connector on the tubular body in contact with a cover to secure the cover to a surface of the stent. The invention also comprises methods of securing a cover to a stent.
In a first embodiment, the cover connector on an expandable tubular body has a first section, a second section, and a third section between the first and second sections. The connector has an open configuration, and a closed configuration in which the first section has at least one bend and the second section has at least one bend, so that the first and second sections are bent together and are directed towards the third section therebetween. The ends of the connector are configured to pierce the cover so that at least a portion of the first and second sections extend through the cover. With the cover pierced by the first and second ends of the connector, the ends of the connector are bent together towards the third section, so that the first and second sections of the connector are adjacent an outer surface of the cover and the third section of the connector is adjacent an inner surface of the cover, to form the closed configuration. A stent assembly of the invention generally comprises a covered stent having at least a portion of the first and second sections of the cover connector extending through a cover, to secure the cover to the stent. In one embodiment the cover connector is configured to draw the lengthwise edges of a stent cover together as the connector is bent from the first to the second configuration to close the cover about the stent surface.
A method of securing a cover to a stent generally comprises piercing the first end of the cover connector at a first location on the cover and piercing the second end of the cover connector through the cover at a second location from an inner surface to an outer surface of the cover. The first and second sections of the cover connector are bent towards the third section to form the closed configuration and secure the cover to the stent.
In a second embodiment, the cover connector presses the cover against a surface of the stent to secure the cover thereto without piercing the cover. The cover connector is secured to an end of the expandable tubular body of the stent, and is configured to fold from an open configuration to a closed configuration in which the connector extends toward a midpoint of the tubular body between the first and second ends of the tubular body and contacts a cover located between the cover connector and a surface of the tubular body of the stent, to secure the cover thereto. The cover connector presses the cover against a surface of the stent to secure the cover thereto without piercing the cover. A method of securing a cover to a stent generally comprises placing a cover on the stent and folding the cover connector from the open configuration to the closed configuration so that at least a section of the cover is in contact with the cover connector and between the cover connector and a surface of the stent.
The cover connectors may be configured to secure a cover to either an inner surface or an outer surface of the tubular body of the stent. In a presently preferred embodiment, a plurality of cover connectors are provided on the stent to connect a cover which extends over a substantial portion, and preferably all of the length of the stent, in order to minimize restenosis in the body lumen.
In one embodiment, a stent is provided with eyelet members having an opening therein configured to receive a securing member such as a suture to thereby secure a cover to the stent.
The cover may be a variety of suitable materials which are preferably expandable, biocompatible, and non-thrombogenic, including autologous tissue, heterologous tissue such as bovine pericardium, porcine pericardium, aortic leaflet, and polymeric materials such as PTFE and polyesters such as DACRON. In a preferred embodiment, the cover is generally cylindrical for corresponding to the tubular framework or the stent.
The stent may be an expandable, tubular framework and may be a conventional self expanding or balloon expandable stent. A variety of stent designs may be used, including stents formed from braided tube, slotted tubes, and coils or closed sinusoidal rings of wire or ribbon, and the like.
Another embodiment of the invention comprises a stent having an expandable tubular body having a first end, a second end, a plurality of cylindrical wall sections defining an open-walled structure, and having a plurality of bar members connected to the tubular body. Each bar member is connected to and extends between longitudinally adjacent cylindrical wall sections. In one embodiment, at least one bar member is between longitudinally adjacent cylindrical wall sections. In one embodiment, the stent is part of a stent assembly including a cover having a first end, a second end, and an intermediate section between the first and second ends. The cover is disposed over at least one section of the stent and under at least a second section of the stent. For example, in one embodiment, an intermediate section of the cover is adjacent to an outer surface of the intermediate wall section of the stent, and the first end and the second end of the cover are adjacent to an inner surface of the cylindrical wall sections at the first and second ends, respectively, of the stent. In an alternative embodiment, the intermediate section of the cover is adjacent to an inner surface of the intermediate cylindrical wall section of the stent, and the first end and the second end of the cover are adjacent to an outer surface of the cylindrical wall sections at the ends of the stent. The cover is disposed between a portion of a cylindrical wall section and a bar member connecting the cylindrical wall section to a longitudinally adjacent cylindrical wall section of the tubular body. Consequently, the stent facilitates attaching the cover to the stent, and the stent assembly having a cover on the stent provides a securely attached cover, and avoids or reduces disadvantageous damage to the cover during attachment. Disposing a section of the ends of the cover between a portion of the stent tubular body and the bar member attached to that portion in accordance with the invention prevents or inhibits displacement of the cover relative to the stent during advancement or deployment of the stent assembly within a patient""s body lumen. The cylindrical wall sections of the stent are thus configured as cover connectors in that the ends of the cover can be disposed between the wall section and the bar members attached thereto, and can be disposed under some wall sections while being disposed over other wall sections, to secure the cover to the stent. In a presently preferred embodiment, the cover is further secured to the stent with securing members such as suture, clips, wires, and the like. In one embodiment the stent has at least one eyelet member with an opening configured to receive a securing member therein to secure a cover to the tubular body.
The stent assembly is implanted in the patient""s body lumen, typically by mounting the stent assembly on the distal extremity of a delivery catheter. Specifically, a tubular stent with a cover disposed about at least part of the stent, and secured thereto by the cover connectors, is mounted on a balloon, for a balloon expandable stent, or on a containing mechanism for a self expandable stent. The catheter is advanced through the body lumen within the patient until the distal extremity of the catheter having the stent assembly is positioned at a desired location therein. The stent assembly is expanded by expanding the balloon or releasing the containing mechanism on which the stent assembly is mounted to anchor the stent assembly within the body lumen. Once the stent assembly is effectively positioned within the body lumen, the expanded balloon may be contracted, e.g. by deflation, and then the delivery catheter may be withdrawn.
The stent having cover connectors of the invention provides for easy attachment of a stent cover onto the stent. This is particularly advantageous in the case of a cover which is impregnated with a therapeutic or diagnostic agent, such as an angiogenesis or antithrombotic agent, just before use or stored in the agent to preimpregnate the cover. The cover connectors allow the impregnated cover to be quickly and easily attached to the stent just before implantation of the stent assembly in the patient""s body lumen. Thereafter, the stent assembly can be positioned at a desired site within the patient""s body lumen, where the cover will release the therapeutic agent.